The discovery of different families of matrix metalloproteinases (MMPs), their relationships, and their individual characteristics have been categorized in several reports. Emonard, H. et al., Cell Molec. Biol. 36, 131-153 (1990); Birkedal-Hansen, H., J. Oral Pathol. 17, 445-451 (1988); Matrisian, L. M., Trends Genet. 6, 121-125 (1990); Murphy, G. J. P. et al., FEBS Lett. 289, 4-7 (1991); Matrisian, L. M., Bioessays 14, 455-463 (1992). Beckett, R. P. et al., DDT 1, 16-26 (1996).
The MMPs are a family of zinc containing endopeptidases which are capable of cleaving large biomolecules, such as the extracellular matrix they are generally secreted in latent form and require activation by proteolytic enzymes, and they are regulated by specific endogenous inhibitors. Three broad groups of MMPs have been delineated: the collagenases which have triple helical interstitial collagen as a substrate, the gelatinases which are proteinases of denatured collagen and Type IV collagen, and the stromelysins which were originally characterized as proteoglycanases but have now been identified to have a broader proteolytic spectrum. Examples of specific MMPs, include, in the collagenases, fibroblast collagenase (MMP-1); in the gelatinases 72 kDa gelatinase (gelatinase A; MMP-2); and in stromelysins include stromelysin 1 (MMP-3). Other MMPs do not fit neatly into the above groups, for example macrophage metalloelastase (MMP-12). Beckett, R. P. et al., DDT 1, 16-26 (1996).
The characterizing feature of diseases involving the MMP enzymes appears to be a stoichiometric imbalance between active enzymes and endogenous inhibitors, leading to excessive tissue disruption, and often degradation. McCachren, S. S., Arthritis Rheum. 34, inflammatory disorders, such as emphysema; cardiovascular disorders, such as atherosclerosis; corneal ulceration; dental diseases such as gingivitis and periodontal disease; and neurological disorders such as multiple sclerosis. Chirivi, R. G. S. et al., Int. J. Cancer, 58, 460-464 (1994); Zucker, S., Cancer Research, 53, 140-146 (1993). In addition, a recent study indicates that MMP-12 is required for the development of smoking-induced emphysema in mice. Science, 277, 2002 (1997).
Apart from the role of these potentially very destructive enzymes in pathology, the MMPs play an essential role in cell regrowth and turnover in healthy tissue. Broad spectrum inhibition of the MMPs in the clinical setting results in musculoskeletal stiffness and pain. H. S. Rasmussen and P. P. McCann, Pharmacol. Ther., 75, 69-75 (1997). This side effect and others associated with broad spectrum inhibition may be enhanced in chronic administration. Thus, it would be advantageous to provide selective MMP inhibitors.
Surprisingly, we have found that the mercaptoacetylamido dipeptide carboxylic acids of the present application are selective inhibitors of MMP-12 compared to their N-methylamide derivatives. Specifically, while known broad spectrum inhibitors having an amide terminus have inhibiting activities with respect to MMP-1, MMP-2, and MMP-3 (PCT Application No. WO 96/11209, published Apr. 18, 1996) the compounds of the present invention are selective for MMP-12 over MMP-1, MMP-2, and MMP-3 compared to their N-methylamide derivatives. These selective inhibitors are useful for the treatment of smoking-induced emphysema. Because they are selective, the compounds of the present application are expected to be useful for long term therapy with less of the complications related to broad spectrum inhibition.
The present invention provides novel mercaptoacetylamido dipeptide carboxylic acids of the formula 
wherein
R1 is selected from the group consisting of hydrogen, C1-C6 alkyl, xe2x80x94(CH2)axe2x80x94CO2R5, xe2x80x94(CH2)axe2x80x94C(O)NH2, xe2x80x94(CH2)4NH2, xe2x80x94(CH2)3xe2x80x94NHxe2x80x94C(NH)NH2, xe2x80x94(CH2)2xe2x80x94S(O)bxe2x80x94CH3, xe2x80x94CH2xe2x80x94OH, xe2x80x94CH(OH)CH3, xe2x80x94CH2xe2x80x94SH, xe2x80x94(CH2)dxe2x80x94Ar1, and xe2x80x94CH2xe2x80x94Ar2;
wherein
a is 1 or 2;
b is 0, 1, or 2;
d is an integer from 0 to 4;
R5 is selected from the group consisting of hydrogen, C1-C4 alkyl, and benzyl;
Ar1 is a radical selected from the group consisting of 
wherein
R6 is from 1 to 2 substituents independently selected from the group consisting of hydrogen, halogen, C1-C4 alkyl, hydroxy, and C1-C4 alkoxy;
R7 is selected from the group consisting of hydrogen, halogen, C1-C4 alkyl, and C1-C4 alkoxy;
Ar2 is a radical selected from the group consisting of 
R2 is selected from the group consisting of C1-C6 alkyl, xe2x80x94(CH2)exe2x80x94CO2R5xe2x80x2, xe2x80x94(CH2)exe2x80x94C(O)NH2, xe2x80x94(CH2)4NH2, xe2x80x94(CH2)3xe2x80x94NHxe2x80x94C(NH)NH2, xe2x80x94(CH2)2xe2x80x94S(O)fxe2x80x94CH3, xe2x80x94CH2xe2x80x94OH, xe2x80x94CH(OH)CH3, xe2x80x94CH2xe2x80x94SH, xe2x80x94(CH2)gxe2x80x94Ar1xe2x80x2, and xe2x80x94(CH2)xe2x80x94Ar2xe2x80x2;
wherein
e is 1 or 2;
f is 0, 1, or 2;
g is an integer from 1 to 4;
R5 is selected from the group consisting of hydrogen, C1-C4 alkyl, and benzyl;
Ar1xe2x80x2 is a radical selected from the group consisting of 
wherein
R6 is from 1 to 2 substituents independently selected from the group consisting of hydrogen, halogen, C1-C4 alkyl, hydroxy, and C1-C4 alkoxy;
R7xe2x80x2 is selected from the group consisting of hydrogen, halogen, C1-C4 alkyl, and C1-C4 alkoxy;
Ar2xe2x80x2 is a radical selected from the group consisting of 
R3 is selected from the group consisting of C1-C6 alkyl, xe2x80x94(CH2)mxe2x80x94W, xe2x80x94(CH2)pxe2x80x94Ar3, xe2x80x94(CH2)kxe2x80x94CO2R9, xe2x80x94(CH2)mxe2x80x94SO2NR8xe2x80x2xe2x80x94Y1, xe2x80x94(CH2)mxe2x80x94Zxe2x80x94Q
wherein
m is an integer from 2 to 8;
is an integer from 0-10;
k is an integer from 1 to 9;
W is phthalimido;
Ar3 is selected from the group consisting of 
wherein
R23 is from 1 to 2 substituents independently selected from the group consisting of hydrogen, halogen, C1-C4 alkyl, and C1-C4 alkoxy;
R8xe2x80x2 is hydrogen or C1-C6 alkyl;
R9 is hydrogen or C1-C6 alkyl;
Y1 is selected from the group consisting of hydrogen, xe2x80x94(CH2)jxe2x80x94Ar4, xe2x80x94N(R24)2, or Y1 and R8xe2x80x2 are taken together with the nitrogen to which they are attached to form N-morpholino, N-piperidino, N-pyrrolidino, or N-isoindolyl;
wherein
j is 0 or 1;
R24 is hydrogen or C1-C6 alkyl;
Ar4 is 
wherein
R25 is from 1 to 3 substituents independently selected from the group consisting of hydrogen, halogen, C1-C4 alkyl, and C1-C4 alkoxy;
Z is selected from the group consisting of xe2x80x94Oxe2x80x94, xe2x80x94NR8xe2x80x94, xe2x80x94C(O)NR8xe2x80x94, xe2x80x94NR8C(O)xe2x80x94, xe2x80x94NR8C(O)NHxe2x80x94, xe2x80x94NR8C(O)Oxe2x80x94, and xe2x80x94OC(O)NHxe2x80x94;
wherein
R8 is hydrogen or C1-C6 alkyl;
Q is selected from the group consisting of hydrogen, xe2x80x94(CH2)nxe2x80x94Y2, and xe2x80x94(CH2)xY3;
wherein
n is an integer from 0 to 4;
Y2 is selected from the group consisting of hydrogen, xe2x80x94(CH2)hxe2x80x94Ar5 and xe2x80x94(CH2)txe2x80x94C(O)OR27 
wherein
Ar5 is selected from the group consisting of 
wherein
R26 is from 1 to 3 substituents independently selected from the group consisting of hydrogen, halogen, C1-C4 alkyl, and C1-C4 alkoxy;
h is an integer from 0 to 6;
t is an integer from 1 to 6;
R27 is hydrogen or C1-C6 alkyl;
x is an integer from 2 to 4;
Y3 is selected from the group consisting of xe2x80x94N(R28)2, N-morpholino, N-piperidino, N-pyrrolidino, and N-isoindolyl;
wherein
R28 is hydrogen or C1-C6 alkyl;
R4 is selected from the group consisting of hydrogen, xe2x80x94C(O)R10, xe2x80x94C(O)xe2x80x94(CH2)qxe2x80x94X and xe2x80x94Sxe2x80x94G
wherein
R10 is selected from the group consisting of hydrogen, C1-C4 alkyl, phenyl, and benzyl;
q is 0, 1, or 2;
X is selected from the group consisting of 
wherein
V is selected from the group consisting of a bond, xe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94S(O)rxe2x80x94, xe2x80x94NR21xe2x80x94, and xe2x80x94NC(O)R22xe2x80x94;
wherein
r is 0, 1, or 2;
R2 is selected from the group consisting of hydrogen, C1-C4 alkyl, and benzyl;
R22 is selected from the group consisting of hydrogen, xe2x80x94CF3, C1-C10 alkyl, phenyl, and benzyl;
R11 is selected from the group consisting of hydrogen, C1-C4 alkyl, and benzyl;
R11xe2x80x2 is selected from the group consisting of hydrogen, C1-C4 alkyl, and benzyl;
G is selected from the group consisting of 
wherein
w is an integer from 1 to 3;
R12 is selected from the group consisting of hydrogen, C1-C6 alkyl, xe2x80x94CH2CH2S(O)uxe2x80x94CH3, and benzyl;
wherein u is 0,1, or 2;
R13 is selected from the group consisting of hydrogen, hydroxy, amino, C1-C6 alkyl, N-methylamino, N,N-dimethylamino, xe2x80x94CO2R17, and xe2x80x94OC(O)R8;
wherein
R17 is hydrogen, xe2x80x94CH2Oxe2x80x94C(O)C(CH3)3, C1-C4 alkyl, benzyl, or diphenylmethyl;
R18 is hydrogen, C1-C6 alkyl or phenyl;
R14 is 1 or 2 substituents independently selected from the group consisting of hydrogen, C1-C4 alkyl, C1-C4 alkoxy, or halogen;
V1 is selected from the group consisting of xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, and xe2x80x94NHxe2x80x94;
V2 is selected from the group consisting ofxe2x80x94Nxe2x80x94 and xe2x80x94CHxe2x80x94;
V3 is selected from the group consisting of a bond and xe2x80x94C(O)xe2x80x94;
V4 is selected from the group consisting of xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NR19xe2x80x94, and xe2x80x94NC(O)R20;
wherein
R19 is hydrogen, C1-C4 alkyl, or benzyl;
R20 is hydrogen, xe2x80x94CF3, C1-C10 alkyl, or benzyl;
R15 is selected from the group consisting of hydrogen, C1-C6 alkyl and benzyl;
R16 is selected from the group consisting of hydrogen and C1-C4 alkyl; and stereoisomers, pharmaceutically acceptable salt, and hydrate thereof.
The present invention further provides a method of treating smoking-induced emphysema in a patient in need thereof comprising administering to the patient an effective amount of a compound of formula (1).
In addition, the present invention provides pharmaceutical compositions comprising an assayable amount of a compound of formula (1) in admixture or otherwise in association with an inert carrier. The present invention also provides a pharmaceutical composition comprising an effective amount of a compound of formula (1) in admixture or otherwise in association with one or more pharmaceutically acceptable carriers or excipients.
As is appreciated by one of ordinary skill in the art the mercaptoacetylamido dipeptide carboxylic acids of formula (1) exist as stereoisomers. Specifically, it is recognized that they exist as stereoisomers at the point of attachment of the substituents R1, R2, R3, and R4, R12, and xe2x80x94NHR15. Where indicated the compounds follow either the (+)- and (xe2x88x92)- designation for optical rotation, the (D)- and (L)- designation of relative stereochemistry, or the Cahn-Ingold-Prelog designation of (R)- and (S)- for the stereochemistry of compounds represented by formula (1) and intermediates thereof. Any reference in this application to one of the compounds of the formula (1) is meant to encompass either specific stereoisomers or a mixture of stereoisomers.
The specific stereoisomers can be prepared by stereospecific synthesis using enantiomerically pure or enantiomerically enriched starting materials which are well known in the art. The specific stereoisomers of amino acid starting materials can be prepared by stereospecific synthesis as is well known in the art or analogously known in the art, such as D. A. Evans, et al. J. Am. Chem. Soc., 112, 4011-4030 (1990); S. Ikegami et al. Tetrahedron, 44, 5333-5342 (1988); W. Oppolzer et al. Tet. Lets. 30, 6009-6010 (1989); Synthesis of Optically Active xcex1-Amino-Acids, R. M. Williams (Pergamon Press, Oxford 1989); M. J. O""Donnell ed.: xcex1-Amino-Acid Synthesis, Tetrahedron Symposia in print, No. 33, Tetrahedron 44, No. 17 (1988); U. Schxc3x6llkopf, Pure Appl. Chem. 55, 1799 (1983); U. Hengartner et al. J. Org. Chem., 44, 3748-3752 (1979); M. J. O""Donnell et al. Tet. Lets., 2641-2644 (1978); M. J. O""Donnell et al. Tet. Lets. 23, 4255-4258 (1982); M. J. O""Donnell et al. J. Am. Chem. Soc., 110, 8520-8525 (1988).
The specific stereoisomers of either starting materials or products can be resolved and recovered by techniques known in the art, such as chromatography on chiral stationary phases, enzymatic resolution, or fractional recrystallization of addition salts formed by reagents used for that purpose. Useful methods of resolving and recovering specific stereoisomers are known in the art and are described in Stereochemistry of Organic Compounds, E. L. Eliel and S. H. Wilen, Wiley (1994) and Enantiomers, Racemates, and Resolutions, J. Jacques, A. Collet, and S. H. Wilen, Wiley (1981).
As used in this application:
a) the term xe2x80x9chalogenxe2x80x9d refers to a fluorine atom, chlorine atom, bromine atom, or iodine atom;
b) the term xe2x80x9cC1-C6 alkylxe2x80x9d refers to a branched or straight chained alkyl radical containing from 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, hexyl, etc.;
c) the term xe2x80x9cC1-C4 alkylxe2x80x9d refers to a saturated straight or branched chain alkyl group containing from 1-4 carbon atoms and includes methyl, ethyl, propyl, isopropyl, n-butyl, s-butyl, isobutyl, and t-butyl;
d) the term xe2x80x9cC1-C4 alkoxyxe2x80x9d refers to a straight or branched alkoxy group containing from 1 to 4 carbon atoms, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, t-butoxy, etc.;
e) the designation xe2x80x9cxe2x80x9d refers to a bond for which the stereochemistry is not designated;
f) the designation xe2x80x9cxe2x80x9d refers to a bond that protrudes forward out of the plane of the page.
g) the designation xe2x80x9cxe2x80x9d refers to a bond that protrudes backward out of the plane of the page.
h) as used in the examples and preparations, the following terms have the meanings indicated: xe2x80x9cgxe2x80x9d refers to grams, xe2x80x9cmgxe2x80x9d refers to milligrams, xe2x80x9cxcexcgxe2x80x9d refers to micrograms, xe2x80x9cmolxe2x80x9d refers to moles, xe2x80x9cmmolxe2x80x9d refers to millimoles, xe2x80x9cnmolexe2x80x9d refers to nanomoles, xe2x80x9cLxe2x80x9d refers to liters, xe2x80x9cmLxe2x80x9d or xe2x80x9cmlxe2x80x9d refers to milliliters, xe2x80x9cxcexcLxe2x80x9d refers to microliters, xe2x80x9cxc2x0 C.xe2x80x9d refers to degrees Celsius, xe2x80x9cRfxe2x80x9d refers to retention factor, xe2x80x9cmpxe2x80x9d refers to melting point, xe2x80x9cdecxe2x80x9d refers to decomposition, xe2x80x9cbpxe2x80x9d refers to boiling point, xe2x80x9cmm of Hgxe2x80x9d refers to pressure in millimeters of mercury, xe2x80x9ccmxe2x80x9d refers to centimeters, xe2x80x9cnmxe2x80x9d refers to nanometers, xe2x80x9cbrinexe2x80x9d refers to a saturated aqueous sodium chloride solution, xe2x80x9cMxe2x80x9d refers to molar, xe2x80x9cmMxe2x80x9d refers to millimolar, xe2x80x9cxcexcMxe2x80x9d refers to micromolar, xe2x80x9cnMxe2x80x9d refers to nanomolar, xe2x80x9cHPLCxe2x80x9d refers to high performance liquid chromatography, xe2x80x9cHRMSxe2x80x9d refers to high resolution mass spectrum, xe2x80x9cDMFxe2x80x9d refers to dimethylformamide, xe2x80x9cxcexcCixe2x80x9d refers to microcuries, xe2x80x9ci.p.xe2x80x9d refers to intraperitoneally, xe2x80x9ci.v.xe2x80x9d refers to intravenously, and xe2x80x9cDPMxe2x80x9d refers to disintegrations per minute;
i) for substituent Z, the designations xe2x80x94C(O)NR8xe2x80x94, xe2x80x94NR8C(O)xe2x80x94, xe2x80x94NR8C(O)NHxe2x80x94, xe2x80x94NR8C(O)Oxe2x80x94, xe2x80x94OC(O)NHxe2x80x94, and xe2x80x94SO2NR8xe2x80x94 refer to the functionalities represented, respectively, by the following formulae showing the attachment of the group (Q): 
these designations are referred to hereinafter as amido, amide, urea, N-carbamoyl, and O-carbamoyl, respectively;
j) the term xe2x80x9cpharmaceutically acceptable saltsxe2x80x9d thereof refers to either an acid addition salt or a basic addition salt.
The expression xe2x80x9cpharmaceutically acceptable acid addition saltsxe2x80x9d is intended to apply to any non-toxic organic or inorganic acid addition salt of the base compounds represented by formula (1) or any of its intermediates. Illustrative inorganic acids which form suitable salts include hydrochloric, hydrobromic, sulphuric, and phosphoric acid and acid metal salts such as sodium monohydrogen orthophosphate, and potassium hydrogen sulfate. Illustrative organic acids which form suitable salts include the mono-, di-, and tricarboxylic acids. Illustrative of such acids are for example, acetic, glycolic, lactic, pyruvic, malonic, succinic, glutaric, fumaric, malic, tartaric, citric, ascorbic, maleic, hydroxymaleic, benzoic, hydroxybenzoic, phenylacetic, cinnamic, salicyclic, 2-phenoxybenzoic, p-toluenesulfonic acid, and sulfonic acids such as methane sulfonic acid and 2-hydroxyethane sulfonic acid. Such salts can exist in either a hydrated or substantially anhydrous form. In general, the acid addition salts of these compounds are soluble in water and various hydrophilic organic solvents, and which in comparison to their free base forms, generally demonstrate higher melting points.
The expression xe2x80x9cpharmaceutically acceptable basic addition saltsxe2x80x9d is intended to apply to any non-toxic organic or inorganic basic addition salts of the compounds represented by formula (1) or any of its intermediates. Illustrative bases which form suitable salts include alkali metal or alkaline-earth metal hydroxides such as sodium, potassium, calcium, magnesium, or barium hydroxides; ammonia, and aliphatic, alicyclic, or aromatic organic amines such as methylamine, dimethylamine, trimethylamine, and picoline.
As with any group of structurally related compounds which possess a particular utility, certain groups and configurations of substituents are preferred for the compounds of formula (1). Preferred embodiments are given below:
The compounds in which R1 is xe2x80x94(CH2)dxe2x80x94Ar1 are preferred;
The compounds in which R1 is xe2x80x94(CH2)dxe2x80x94Ar1 and Ar1 is the radical 
xe2x80x83and d is 1 and 2 are more preferred;
Compounds in which R2 is selected from the group consisting of C1-C6 alkyl, xe2x80x94(CH2)4NH2, xe2x80x94(CH2)2xe2x80x94S(O)fxe2x80x94CH3, and xe2x80x94(CH2)gxe2x80x94Ar1xe2x80x2 are preferred;
Compounds in which R3 is selected from the group consisting of C1-C6 alkyl, and xe2x80x94(CH2)mxe2x80x94W are preferred;
Compounds in which R3 is 2-propyl are more preferred;
Compounds in which R4 is hydrogen, xe2x80x94C(O)R10 and xe2x80x94Sxe2x80x94G are preferred;
Compounds in which R4 is xe2x80x94C(O)R10 and R10 is C1-C4 alkyl more preferred;
Compounds in which R4 is xe2x80x94Sxe2x80x94G and G is a radical selected from the group 
are more preferred.
Examples of compounds encompassed by the present invention include the following. It is understood that the examples encompass all of the isomers of the compound and mixtures thereof. This list is meant to be representative only and is not intended to limit the scope of the invention in any way:
2-mercapto-pentanoyl-homo-phenylalanyl-phenylalanine;
2-mercapto-pentanoyl-leucyl-phenylalanine;
2-mercapto-pentanoyl-methionyl-phenylalanine;
2-mercapto-pentanoyl-lysyl-phenylalanine;
2-mercapto-pentanoyl-t-leucyl-phenylalanine;
2-mercapto-3-methylbutyroyl-homo-phenylalanyl-phenylalanine;
2-mercapto-3-methylbutyroyl-leucyl-phenylalanine;
2-mercapto-3-methylbutyroyl-methionyl-phenylalanine;
2-mercapto-3-methylbutyroyl-lysyl-phenylalanine;
2-mercapto-3-methylbutyroyl-t-leucyl-phenylalanine;
2-thioacetyl-pentanoyl-homo-phenylalanyl-phenylalanine;
2-thioacetyl-pentanoyl-leucyl-phenylalanine;
2-thioacetyl-pentanoyl-methionyl-phenylalanine;
2-thioacetyl-pentanoyl-lysyl-phenylalanine;
2-thioacetyl-pentanoyl-t-leucyl-phenylalanine;
2-thioacetyl-3-methylbutyroyl-homo-phenylalanyl-phenylalanine;
2-thioacetyl-3-methylbutyroyl-leucyl-phenylalanine;
2-thioacetyl-3-methylbutyroyl-methionyl-phenylalanine;
2-thioacetyl-3-methylbutyroyl-lysyl-phenylalanine; and
2-thioacetyl-3-methylbutyroyl-leucyl-phenylalanine.
The compounds of formula (1) can be prepared by a variety of procedures readily known to those skilled in the art. Such procedures include, peptide coupling, such as solid phase sequential procedures and solution phase sequential procedures using suitable amino acids and substituted acids and displacement, modification, and functionalization procedures, as required, utilizing suitable protecting groups and deprotection procedures.
As used herein the term xe2x80x9camino acidxe2x80x9d refers to naturally occurring amino acids as well as non-naturally occurring amino acids having substituents encompassed by R1 and R2 as described above. The naturally occurring amino acids included are glycine, alanine, valine, leucine, isoleucine, serine, methionine, threonine, phenylalanine, tyrosine, tryptophan, cysteine, histidine, aspartic acid, asparagine, glutamic acid, glutamine, arginine, ornithine, and lysine. Non-naturally occurring amino acids within the term xe2x80x9camino acid,xe2x80x9d include without limitation, the D-isomers of the naturally occurring amino acids, norleucine, norvaline, alloisoleucine, t-butylglycine, methionine sulfoxide, and methionine sulfone. Other non-naturally occurring amino acids within the term xe2x80x9camino acid,xe2x80x9d include without limitation phenylalanines substituted by R6 and R6xe2x80x2 as described above; phenylglycines, homophenylalanines, 3-phenylpropylglycines, 4-phenylbutylglycines; including those substituted by R6 and R6xe2x80x2 as described above; and 2-naphthylalanines, including those substituted by R7 and R7xe2x80x2 as described above.
Solid phase sequential procedures can be performed using established methods, including automated methods such as by use of an automated peptide synthesizer. Steward and Young, Solid Phase Peptide Synthesis (Freeman 1969) and B. Merrifield, Peptides: Synthesis, Structures, and Applications (B. Gutte, Ed., Acedemic Press 1995). In this procedure a protected amino acid bearing R1 or protected R1 is bound to a resin support. The resin support employed can be any suitable resin conventionally employed in the art for the solid phase preparation of poly-peptides, preferably polystyrene which has been crossed away with about 0.5 to about 3 percent divinyl benzene, which has been either in chloromethylated or hydroxymethylated to provide sites for ester formation with the initially introduced protected amino acid. Suitable resins are well known and appreciated in the art, including those described in Rink, Tet. Let., 28, 3787 (1987) and Sieber, Tet. Let., 28, 2107 (1987). Included within the solid phase methods are combinatorial methods which are known in the art. K. S. Lam, Chem. Rev., 97, 411-448 (1997).
In a subsequent step the resin-bound protected amino acid is sequentially amino deprotected and coupled with a protected amino acids bearing R2 or protected R2 to give a resin-bound protected dipeptide. This resin bound protected dipeptide is sequentially amino deprotected and coupled with a protected amino acid bearing R3 or protected R3 to give a protected tripeptide. Alternately, an appropriate protected dipeptide may be coupled by the solution method prior to coupling with the resin-bound amino acid.
Each protected amino acids or amino acid sequence is introduced into the solid phase reactor and about a two-fold to four-fold excess. The coupling is carried out in a suitable medium, for example dimethylformamide, dichloromethane, or mixtures of dimethylformamide and dichloromethane. As is well known and appreciated in the art, wherein complete coupling occurs, the coupling in procedure is repeated before removal of the protecting group, prior to the coupling of the next amino acids in the solid phase reactor.
After the compound of formula (1) or protected compound of formula (1) has been obtained it is removed from the resin under conditions well known in the art. For example, removal can be accomplished by treatment of the resin bound compound with a solution of 5% anisole in anhydrous hydrofluoric acid, 95% trifluoroacetic acid/4% water/1% 2-mercaptoethanol solution, or other procedures as are appropriate depending on the resin used.
Compounds of formula (1) obtained by solid phase sequential procedures can be purified by procedures well known and appreciated in the art, such as chromatography, lyophilzation, trituration, salt formation, and crystallization.
The compounds of formula (1) can also be prepared by solution phase sequential procedures well known and appreciated in the art. Accordingly, suitably protected amino acids, substituted acids or dipeptides are coupled by procedures requiring activation of the carbonyl group and coupling reaction with amine function of an appropriate protected amino acid or dipeptide. These procedures are well known appreciated in the art.
Specifically, a carbonyl protected amino acid bearing R1 or protected R1 is coupled with an amino protected amino acid bearing R2 or protected R2, followed by a selective amino deprotection, and coupling with an acid bearing R3 or protected R3 and xe2x80x94SR4, or a functionality which gives rise to xe2x80x94SR4 upon deprotection and modification or displacement and further modification, if desired. Alternately, a carbonyl protected dipeptide bearing a R1 or protected R1 amino acids residue at the carbonyl end a R2 or protected R2 amino acids residue at amino end is coupled an amino protected amino acid bearing R3 or protected R3 and xe2x80x94SR4, or a functionality which gives rise to xe2x80x94SR4 upon deprotection and modification or displacement and further modification, if desired.
The selection of an appropriate coupling reagent is within the skill of the art. A particularly suitable coupling reagent where the amino acid to be added is glutamine, asparingine, or aspratamine is N,Nxe2x80x2-diisopropylcarbodiimide and 1-hydroxy-benzotriazole. The use of these reagents prevents nitrile and lactam formation. Other coupling agents are carbodiimides (e.g., N,Nxe2x80x2-dicyclohexylcarbodiimide and N-ethyl-Nxe2x80x2-(3-dimethylaminopropylcarbodiimide); cyanamides (e.g., N,N-dibenzylcyanamide); (3) ketenimines; isoxazolium salts (e.g., N-ethyl-5-phenyl-isoxazolium-3xe2x80x2-sulfonate; monocyclic nitrogen containing heterocyclic amides of aromatic character containing one through four nitrogens in the ring such as imidazolides, pyrazolides, and 1,2,4-triazolides. Specific heterocyclic amides that are useful include N,Nxe2x80x2-carbonyldiimidazole and N,N-carbonyl-di-1,2,4-triazole; alkoxylated acetylene (e.g., ethoxyacetylene); reagents which form a mixed anhydride with the carboxyl moiety of the amino acid (e.g., ethylchloroformate and isobutylchloroformate) or the symmetrical anhydride of the amino acid to be coupled (e.g., Boc-phenylalanine-O-phenylalinine-Boc) and nitrogen containing heterocyclic compounds having a hydroxy group on one ring nitrogen (e.g., N-hydroxyphthalimide, N-hydroxysuccinimide and 1-hydroxybenzotriazole). Other activating reagents and their use in peptide coupling are described by Kapoor, J. Pharm. Sci., 59, 1-27 (1970). When using the solid phase method, Applicants prefer the use of use of the symmetrical anhydride as a coupling reagent for all amino acids except arginine, asparamine and glutamine.
In coupling individual amino acids, substituted acids, or peptides as described above the selection and use of appropriate protecting groups for R1, R2, R3, or the thiol ultimately bearing R4 is within the ability of those skilled in the art and will depend on the amino acid to be protected in the presence of other protected amino acids residues, thiol protecting groups, and subsequent displacement or modification reactions as are required.
In carrying out the procedures described herein, suitable protecting groups with each amino acid introduced may be any of amino acid protecting groups known in the art. Suitable amino protecting groups include, acyl type protecting groups such as: formyl, trifluoroacetyl, 4-chlorobutyryl, phthalyl, and o-nitrophenoxyacetyl and, sulfonyl type protecting groups such as toluenesulfonyl(tosyl), benzenesulfonyl, nitro-phenylsulfenyl, and tritylsulfenyl; aromatic urethane type protecting groups such as benzyloxycarbonyl and substituted benzyloxycarbonyl, such as p-chlorobenzyloxycarbonyl, p-nitrobenzyloxycarbonyl, p-bromobenzyl-oxycarbonyl, p-methoxybenzyloxycarbonyl, 1-(p-biphenylyl)-1-methylethoxycarbonyl, and benzhydryloxycarbonyl; aliphatic urethane protecting groups such as tert-butyloxycarbonyl(t-Boc), diisopropylmethoxycarbonyl, isopropyloxycarbonyl, ethoxycarbonyl and allyloxycarbonyl; cycloalkyl urethane type protecting groups such as cyclopentyloxycarbonyl, adamantyloxycarbonyl, and cyclo-hexyloxycarbonyl; thio urethane type protecting groups such as phenylthiocarbonyl; alkyl type protecting groups such as triphenylmethyl(trityl) and benzyl; and trialkylsilane groups such as trimethylsilane. The preferred amino protecting group is tert-butyloxycarbonyl.
As is appreciated by those skill in the art, many of the amino acids require protection during such sequential procedures. The use and selection of appropriate protecting groups is within the ability of those skilled in the art and will depend upon them amino acid to be protected in the presence of other protected amino acid residues or other protecting groups. For example, the selection of such a side chain protecting group is critical in that it must be one which is not removed during cleavage of the protecting group of the amino moiety. For example, the carboxylic group of aspartic acid and glutamic acid can be protected with a benzyl or cyclohexyl group. The preferred protecting group is benzyl. For example, when t-Boc is used as the a-amino protecting group, the following side chain protecting groups are suitable: p-toluenesulfonyl can be used to protect amino containing side chain; p-methoxybenzyl, benzyl, acetyl, benzoyl, t-butylsulfonyl moieties can be used to protect thiol containing side chains; benzyl and cyclohexyl can be used to protect carboxylic acid containing side chains; benzyl can be used to protect the hydroxy of hydroxyalkyl containing side chains, and 2-bromocarbobenzyloxy can be used to protect the hydroxy of hydroxyaromatic containing side chains.
The compounds of formula (1) can be prepared by utilizing techniques and procedures well known and appreciated by one of ordinary skill in the art. To further illustrate, general synthetic schemes for preparing intermediates and the compounds of formula (1) are set forth below. In the reaction schemes below, the reagents and starting materials are readily available to one of ordinary skill in the art and all substituents are as previously defined unless otherwise indicated. 
In Scheme A, step 1, an appropriate amino protected amino acid derivative of the formula (1a1) or a salt thereof is coupled with an appropriate carboxy protected amino acid of the formula (2a1) to give, after amino deprotection (step 2), a dipeptide of formula (2).
An appropriate compound of the formula (1a1) is one in which R2 is as desired in the final compound of formula (1) or gives rise after deprotection to R2 as desired in the final compound of formula (1). In addition, an appropriate compound of the formula (1a1) may also be one in which the stereochemistry at the R2 bearing carbon is as desired in the final product of formula (1). The amino protecting group (Pg2) is one which can be selectively removed in the presence of Pg1 and any protecting groups on R1 and/or R2. The use of t-Boc and F-moc for Pg2 is preferred. The activating group (A) is one which undergoes an amidation reaction. As is well known in the art an amidation reaction may proceed through an acid, A is xe2x80x94OH; or an acid may be first converted to an acid chloride, A is xe2x80x94Cl; or an activated intermediate; such as an anhydride; a mixed anhydride of aliphatic carboxylic acid, such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, pivalic acid, 2-ethylbutyric acid, trichloroacetic acid, trifluoroacetic acid, and the like; of aromatic carboxylic acids, such as benzoic acid and the like; of an activated ester, such as phenol ester, p-nitrophenol ester, 2,4-dinitrophenol ester, pentafluorophenol ester, pentachlorophenol ester, N-hydroxysuccinimide ester, N-hydroxyphthalimide ester, 1-hydroxy-1H-benztriazole ester, and the like; activated amide, such as imidazole, dimethylpyrazole, triazole, or tetrazole; or an intermediate formed in the presence of coupling agents, such as dicyclohexylcarbodiimide or 1-(3-dimethyaminopropyl)-3-ethylcarbodiimide. Acid chlorides and activated intermediates may be prepared but are not necessarily isolated before the addition of an appropriate amine of formula (1a1) or a salt thereof.
An appropriate compound of the formula (2a1) is one in which R1 is as desired in the final compound of formula (1) or gives rise after deprotection to R1 as desired in the final compound of formula (1). In addition, an appropriate compound of formula (2a1) may also be one in which the stereochemistry at the R1 bearing carbon is as desired in the final product of formula (1). The carboxy protecting group (Pg1) is one which allows for selective removal of the amino protecting group (Pg2) and does not interfere with subsequent deprotection, displacement, derivitivization, functionalization, or modification reactions, as are required. The carboxy protecting group (Pg1) may also be an attachment to a suitable resin. For solution phase couplings the use of the carboxy protecting groups, such as methyl, t-butyl, cyclohexyl, benzyl, and diphenylmethyl are preferred.
Such peptide coupling reactions are carried out in suitable solvents and using suitable bases and coupling reagents, as required, and are well known and appreciated in the art. The product of Reaction Scheme A, step 1, can be isolated and purified by techniques well known in the art, such as extraction, evaporation, trituration, lyophilization, chromatography, and recrystallization. Alternately, the product of Reaction Scheme A, step 1, can be used directly in step 2 after isolation and without further purification.
In Reaction Scheme A, step 2, the amino protecting group (Pg2) of the product of coupling step 1 is selectively removed to give the dipeptide of formula (2). Such selective amino deprotection reactions are well known and appreciated in the art. The product of Reaction Scheme A, step 2, can be isolated and purified by techniques well known in the art, such as extraction, evaporation, salt formation, trituration, lyophilization, chromatography, and recrystallization.
In Reaction Scheme A, step 3, a dipeptide of formula (2) coupled with an appropriate acid derivative bearing R3xe2x80x2 and Y (compound of formula (3b1)) to give a compound of formula (4). Such coupling reactions are well known and appreciated in the art and discussed above. The product of Reaction Scheme A, step 3, can be isolated and purified by techniques well known in the art and described in Reaction Scheme A, step 1, above.
An appropriate compound of formula (3b1) is one in which R3xe2x80x2 is R3 as desired in the final product of formula (1) or gives rise after deprotection to R3 as desired in the final product of formula (1) and Y is a protected thio substituent or Y may be a protected hydroxy substituent or bromo which gives rise upon selective deprotection and displacement or displacement and further deprotection and/or elaboration, if required, to xe2x80x94SR4 as desired in the final product of formula (1) (Reaction Scheme C). Alternately, an appropriate compound of formula (3b1) may also be one in which R3xe2x80x2 gives rise to R3xe2x80x3 which, upon derivatization, gives rise R3 as desired in the final product of formula (1) and Y is a protected thio substituent. The activating group (A) is as described in Reaction Scheme A, step 1, above (Reaction Scheme D). In addition, an appropriate compound of formula (3b1) may also be one in which the stereochemistry at the R3xe2x80x2 and Y bearing carbon is as desired in the final product of formula (1) or gives rise after displacement to the stereochemistry as desired at that carbon in the final product of formula (1).
The use and selection of appropriate protecting groups is within the ability of those skilled in the art and will depend upon compound of formula (3b1) to be protected, the presence of other protected amino acid residues, other protecting groups, and the nature of the particular R3 and/or R4 group(s) ultimately being introduced. Compounds of formula (3b1) in which Y is bromo and protected thio are commercially available or can be prepared utilizing materials, techniques, and procedures well known and appreciated by one of ordinary skill in the art or described herein. See PCT Application WO 96/11209, published Apr. 18, 1996. Examples commercially available compounds of formula (3b1) in which Y is bromo include 2-bromopropionic acid, 2-bromobutyric acid, 2-bromovaleric acid, 2-bromohexanoic acid, 6-(benzoylamino)-2-bromohexanoic acid, 2-bromoheptanoic acid, 2-bromooctanoic acid, 2-bromo-3-methylbutyric acid, 2-bromoisocaproic acid, 2-bromo-3-(5-imidazoyl)proionic acid, (R)-(+)-2-bromopropionic acid, (S)-(xe2x88x92)-2-bromopropionic acid.
In addition, an appropriate compound of formula (3b1) may also be one in which the stereochemistry at the R3 and Y bearing carbon is as desired in the final product of formula (1) or gives rise after displacement to the stereochemistry as desired at that carbon in the final product of formula (1). The activating group (A) is as described in Reaction Scheme A, step 1, above.
The versatile intermediate of formula (4) can also be prepared as set forth below in Reaction Scheme B. 
In Scheme B, step 1, an appropriate carboxy protected amino acid derivative bearing R2 or protected R2 (compound of the formula (2a2)) is coupled with an appropriate acid derivative bearing R3xe2x80x2 and Y (compound of formula (3b2)), to give after carboxy deprotection (step 2), a compound of formula (4c). Such coupling reactions are carried out in suitable solvents and using suitable bases and coupling agents, as required, and are well known and appreciated in the art and discussed above. The product of Reaction Scheme B, step 1, can be isolated and purified by techniques well known in the art or can be used directly in step 2.
An appropriate compound of the formula (2a2) is one in which R2 is as desired in the final compound of formula (1) or gives rise after deprotection to R2 as desired in the final compound of formula (1). In addition, an appropriate compound of the formula (2a2) may also be one in which the stereochemistry at the R2 bearing carbon is as desired in the final product of formula (1). The carboxy protecting group (Pg1xe2x80x2) is one which can be selectively removed in the presence of any protecting groups on R2, R3xe2x80x2, and/or Y. The use of methyl, benzyl, and t-butyl for Pg1xe2x80x2 is preferred.
An appropriate compound of formula (3b2) is one in which R3xe2x80x2 and Y are as defined in Reaction Scheme A, step 3, above. In addition, an appropriate compound of formula (3b2) may also be one in which the stereochemistry at the R3xe2x80x2 and Y bearing carbon is as desired in the final product of formula (1) or gives rise after displacement to the stereochemistry as desired at that carbon in the final product of formula (1). The activating group (A) is as described in Reaction Scheme A, step 1, above.
In Reaction Scheme B, step 2, the carboxy protecting group (Pg1xe2x80x2) of the product of coupling step 1 is selectively removed to give the compound of formula (4c). Such selective carboxy deprotection reactions are well known and appreciated in the art. The product of Reaction Scheme B, step 2, can be isolated and purified by techniques well known in the art, such as extraction, evaporation, salt formation, trituration, lyophilization, chromatography, and recrystallization or can be used directly in the following step.
In Reaction Scheme B, step 3, an appropriate carboxy protected amino acid derivative bearing R1 or protected R1 (compound of the formula (1 a2)) is coupled with a compound of formula (4c) to give a compound of formula (4). Such coupling reactions are carried out as discussed above.
An appropriate compound of the formula (1a2) is one in which R1 is as desired in the final compound of formula (1) or gives rise after deprotection to R1 as desired in the final compound of formula (1). In addition, an appropriate compound of formula (1a2) may also be one in which the stereochemistry at the R1 bearing carbon is as desired in the final product of formula (1). The carboxy protecting group (Pg1) is as defined in Reaction Scheme A, step 1.
In Reaction Scheme C an intermediate of formula (4) in which R3xe2x80x2 is R3 as desired in the final product of formula (1) or gives rise after deprotection to R3 as desired in the final product of formula (1) and Y is a protected thio substituent or a hydroxy substituent or bromo gives rise to a final product of formula (1). 
In Reaction Scheme C, step 1, a compound of formula (4) in which Y is protected thio gives rise upon selective deprotection to give a compound of formula (5a).
For example, compounds of formula (4) in which Y is a protected thio substituent, are selectively deprotected to give a thiol of formula (5a). Protected thio substituents include thioesters, such as thioacetyl or thiobenzoyl, thioethers, such as thiobenzyl, thio-4-methoxybenzyl, thiotriphenylmethyl, or thio-t-butyl, or unsymmetrical sulfides, such as dithioethyl or dithio-t-butyl. The use and selective removal of such thio protecting groups is well known and appreciated in the art and described in Protective Groups in Organic Synthesis, Theodora W. Greene (Wiley-Interscience, 2nd Edition, 1991).
Also encompassed by Reaction Scheme C, step 1, a compound of formula (4) in which Y is hydroxy (obtained from protected hydroxy compounds of formula (4)) undergoes a displacement reaction with an appropriate thio introducing reagent by the method of Mitsunobu to give a compound of formula (4) in which Y is a protected thio substituent or xe2x80x94SR4 as desired in the final compound of formula (1). For example, a compound of formula (4) in which Y is hydroxy reacts with thioacetic acid or thiobenzoic acid, triphenylphosphine, and diethylazodicarboxylate in a suitable aprotic solvent, such as tetrahydrofuran to give a compound of formula (4) in which Y is thioacetyl or thiobenzoyl. Selective removal of the thioacetic acid or thiobenzoic acid moiety gives the desired compound of formula (5a). The product can be isolated and purified by techniques well known in the art, such as extraction, evaporation, trituration, lyophilization, chromatography, and recrystallization.
Also, in Reaction Scheme C, step 1, a compound of formula (4) in which Y is bromo undergo a displacement reaction with an appropriate thio introducing reagent to give a compound of formula (4) in which Y is protected thio substituent which gives rise upon deprotection and subsequent elaboration, if desired, the xe2x80x94SR4 as desired in the final compound of formula (1). An appropriate thio introducing reagent is also one which introduces a group xe2x80x94SR4 as desired in the final compound of formula (1).
For example, a solution of p-methoxybenzylmercaptan in a suitable organic solvent such as dimethylformamide is degassed and treated with a suitable base such as sodium hydride. After about 1 to 2 hours, a solution of a compound of formula (4) in which Y is bromo is added. The reaction may benefit from the addition of a suitable catalyst, such as tetra-n-butylammonium iodide. The reaction mixture is carried out for 1 to 25 hours at temperatures ranging form 0xc2x0 C. to about 100xc2x0 C. Selective removal of the 4-methoxybenzyl moiety gives the desired compound of formula (5a). The product can be isolated and purified by techniques well known in the art, such as extraction, evaporation, trituration, lyophilization, chromatography, and recrystallization.
In Reaction Scheme C, step 2, a compound of formula (5a) undergoes modification reaction to give a compound of formula (6). Such modification reactions include, thiol esterification and disulfide formation.
Compounds of formula (6) in which R4 is xe2x80x94C(O)R10 or xe2x80x94C(O)xe2x80x94(CH2)qxe2x80x94X group can be synthesized by thiol esterifications according to techniques well known and appreciated by one of ordinary skill in the art, such as those disclosed in U.S. Pat. No. 5,424,425, issued Jun. 13, 1995.
For example, in a thiol esterification a compound of formula (5a) is contacted with about an equimolar amount of an appropriate acid, such as HOxe2x80x94C(O)R10 or HOxe2x80x94C(O)xe2x80x94(CH2)qxe2x80x94X in the presence of a suitable coupling agent to give a compound of formula (6) in which R4 is xe2x80x94C(O)R10 or xe2x80x94C(O)xe2x80x94(CH2)qxe2x80x94X. The reaction is carried out in the presence of a coupling agent such as 2-fluoro-1-methylpyridinium p-toluenesulfate, EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride), carbonyldiimidazole, EEDQ (1-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline, DCC, or diethylcyanophosphonate in a suitable aprotic solvent such as methylene chloride. The reaction is generally carried out at temperature of between xe2x88x9220xc2x0 C. and the boiling point of the solvent. Generally, the reaction requires 1 to 24 hours. The product can be isolated and purified by techniques well known in the art, such as extraction, evaporation, trituration, lyophilization, chromatography, and recrystallization.
Compounds of formula (6) in which R4 is xe2x80x94Sxe2x80x94G group can be synthesized according to techniques well known and appreciated by one of ordinary skill in the art, as disclosed in PCT Application No. WO 95/21839, published Aug. 17, 1995 and U.S. Pat. No. 5,491,143, issued Feb. 13, 1996, and U.S. Pat. No. 5,731,306, issued Mar. 24, 1998, and Roques, B. P. et al., J. Med. Chem. 33, 2473-2481 (1992).
For example, in a disulfide formation a compound of formula (5a) is contacted with an appropriate compound of formula (7). 
An appropriate compound of formula (7) is one which gives G as desired in the final product of formula (1) or gives rise upon deprotection to G as is desired in the final product of formula (1). In addition, the compound of formula (7) may have stereochemistry as desired in the final product of formula (1). The reaction is carried out in a suitable solvent, such as ethanol, methanol, dichloromethane, or mixtures of ethanol or methanol and dichloromethane. The solvent is degassed by passing a stream of nitrogen gas through it for 15 minutes before the reaction is carried out. The reaction is carried out using from 1.0 to 4.0 molar equivalents of an appropriate compound of formula (7). The reaction is carried out at temperatures of from 0xc2x0 C. to the refluxing temperature of the solvent, with a temperature of 10xc2x0 C. to 30xc2x0 C. being preferred. The reaction generally requires from 1 to 48 hours. The product can be isolated by techniques well known in the art, such as extraction, evaporation, and precipitation and can be purified by chromatography and recrystallization.
In Reaction Scheme C, step 3, a compound of formula (4) in which Y is hydroxy or bromo can be displaced by an appropriate thiol, HSR4, by the methods described in Reaction Scheme C, step 1, to give a compound of formula (6). In Reaction Scheme C, step 3, an appropriate thiol HSR4 is one which gives R4 as desired in the final product of formula (1) or gives rise to R4 as desired in the final product of formula (1). In addition, a compound of formula (4) in which Y is bromo can be displaced by an appropriate thio ester, Ph3Sxe2x80x94C(O)xe2x80x94(CH2)qxe2x80x94X by techniques well known and appreciated in the art, as disclosed in U.S. Pat. No. 5,424,425, issued Jun. 13, 1995.
In Reaction Scheme C, step 4, a compound of formula (5), (5a), or (6) is deprotected to give a compound of formula (1). Such deprotection reactions are well known appreciated in the art and may include selective deprotections in which the carboxy protecting group (Pg1) and protecting groups on R1, R2, R3, and R4 are removed if desired.
In Reaction Scheme D an intermediate of formula (4) in which R3xe2x80x2 gives rise to R3xe2x80x3 and Y is xe2x80x94SR4 as is desired in the final product of formula (1) or a protected thio substituent gives a compound of formula (1). 
In Reaction Scheme D, step 1, an appropriate compound of formula (4) is deprotected, hydrolyzed, or reduced to give a compound of formula (4a). In Reaction Scheme D, step 1, an appropriate compound of formula (4) is one in which R3xe2x80x2 gives rise to a compound of formula (4a) in which R3xe2x80x3 is R3 as desired in the final product of formula (1) or undergo further derivitization (step 2) to give a compound of formula (5) in which R3 is a desired in the final product of formula (1). In Reaction Scheme D, step 1, an appropriate compound of formula (4) is one in which Y is xe2x80x94SR4 as desired in the final compound of formula (1) or Y gives rise upon deprotection (step 5) and further functionalization (step 4) to give xe2x80x94SR4, as desired, in the final product of formula (1).
For example, in a deprotection a compound of formula (4) in which R3xe2x80x2 is xe2x80x94(CH2)mxe2x80x94W (phthalimido group) is contacted with a molar excess of hydrazine monohydrate to give a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x80x94NHR8 in which R8 is hydrogen. The reaction is typically carried out in a protic organic solvent, such as methanol or ethanol. The reaction is generally carried out at room temperature for a period of time ranging from 5-24 hours. The product can be isolated by techniques well known in the art, such as extraction, evaporation, and precipitation and can be purified by chromatography and recrystallization.
Alternately, for example, in a deprotection a compound of formula (4) in which R3xe2x80x2 is xe2x80x94(CH2)mxe2x80x94NR8-t-Boc is contacted with a molar excess of a suitable acid to give a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x80x94NHR8. The reaction is typically carried out in a organic solvent, such as methanol, ethanol, ethyl acetate, diethyl ether, or dioxane. Suitable acids for this reaction are well known in the art, including hydrochloric acid, hydrobromic acid, trifluoroacetic acid, and methanesulfonic acid. The reaction is generally carried out at room temperature for a period of time ranging from 1-10 hours. The product can be isolated by techniques well known in the art, such as extraction, evaporation, and precipitation and can be purified by chromatography and recrystallization.
For example, in a hydrolysis a compound of formula (4) in which R3xe2x80x2 is xe2x80x94(CH2)mxe2x80x94C(O)OPg3 and Pg3 is methyl or ethyl is contacted with about 1 to 2 molar equivalents of lithium hydroxide, sodium hydroxide, or potassium hydroxide to give a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x80x94CO2H. The reaction is carried out in a suitable solvent, such as methanol, ethanol methanol/water mixtures, ethanol/water mixtures, or tetrahydrofuran/water mixtures and generally requires 1 to 24 hours. The reaction is carried out at temperatures of from about 0xc2x0 C. to the refluxing temperature of the solvent. The resulting acid is isolated and purified by techniques well known in the art, such as acidification, extraction, evaporation, and precipitation and can be purified by trituration, precipitation, chromatography, and recrystallization.
For example, in a reduction a compound of formula (4a) in which R3xe2x80x2 is xe2x80x94(CH2)mxe2x88x921xe2x80x94CO2Pg3 in which Pg3 is methyl or ethyl is contacted with a suitable reducing agent, such as lithium borohydride, lithium aluminum hydride, diisobutylaluminum hydride, 9-borabicyclo[3.3.1]nonane, preferably lithium borohydride to provide a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x88x921xe2x80x94CH2OH. The reaction is carried out in a suitable solvent, such as dichloromethane, tetrahydrofuran, or toluene, with tetrahydrofuran being preferred. The reaction is carried out at a temperature of from about xe2x88x9230xc2x0 C. to about 50xc2x0 C. and generally requires from 2 to 12 hours. The product can be isolated by quenching, extraction, evaporation, and precipitation and can be purified by trituration, chromatography, and recrystallization.
In Reaction Scheme D, step 2, a compound of formula (4a) undergoes a derivitization reaction to give a compound of formula (5) in which R3 is as desired in the final product of formula (1). Such derivitization reactions include hydrolysis of esters and ester formations as are well known in the art, ether formation, amine alkylation, formation of amides, urea formation, carbamate formation, and formation of sulfonamide. In Reaction Scheme D, step 2, the compound of formula (4a) is one in which Y is a protected thio group, such as thioacetyl, thiobenzoyl, 4-methoxybenzyl thiol or t-butylthiol.
For example, in an ether formation a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x88x921xe2x80x94CH2OH is contacted with 1 to 10 molar equivalents of a suitable akylating agent to give a compound of formula (5) in which R3 is xe2x80x94(CH2)mxe2x80x94Zxe2x80x94Q in which Z is xe2x80x94Oxe2x80x94. A suitable alkylating agent is one which transfers Q or protected Q as desired in the final product of formula (1), such as benzyl bromide, benzyl chloride, substituted benzyl bromide, substituted benzyl chloride, ethyl bromoacetate, t-butyl bromoaceate, ethyl 3-chloropropionate, ethyl 3-bromopropionate, ethyl 5-bromovalerate, ethyl 4-bromobutyrate, 3-chloropropionamide, 2-bromoethylbenzene, substituted 2-bromoethylbenzene, 1-chloro-3-phenylpropane, 1-bromo-4-phenylbutane, and the like, or nitrogen mustards, including 2-dimethylaminoethyl chloride, 2-diethylaminoethyl chloride, and 3-dimethylaminopropyl chloride. The reaction is carried out in a suitable solvent, such as diethyl ether, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, or acetonitrile and using a suitable base, such as sodium hydride, potassium hydride, potassium t-butoxide, and lithium diisopropylamide. The reaction is generally carried out at temperatures of xe2x88x9270xc2x0 C. and room temperature and require from about 1-24 hours. The product can be isolated by techniques well known in the art, such as extraction, evaporation, and precipitation and can be purified by chromatography and recrystallization.
Alternately, as appreciated by those skilled in the art, an ether formation can also be carried out by a procedure similar to the one above using a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x88x921xe2x80x94CH2OH in which the hydroxy group is first converted to a leaving group, such as chloro, bromo, or mesylate and a suitable alcohol which transfers Q or protected Q as desired in the final product of formula (1), such as benzyl alcohol, substituted benzyl alcohol, phenol, substituted phenol, and the like. The conversion of hydroxy to leaving groups, such as chloro, bromo, and mesylate are well known and appreciated in the art.
For example, in an amine alkylation a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x80x94NHR8 is contacted with 1 to 10 molar equivalents of a suitable alkylating agent to give a compound of formula (5) in which R3 is xe2x80x94(CH2)mxe2x80x94Zxe2x80x94Q in which Z is xe2x80x94NR8xe2x80x94. The reaction may be carried out after protection of the amine function of R3xe2x80x3 in which R8 is hydrogen by a suitable protecting group, such as benzyl or t-Boc. For an amine alkylation a suitable alkylating agent is one as described above for the ether formation and also includes alkylhalides, such as methyl iodide, methyl bromide, ethyl bromide, propyl bromide, propyl chloride, butyl bromide, butyl chloride, and the like. The reaction is carried out in a suitable solvent, such as methanol, ethanol, dimethylformamide, or pyridine and using a suitable base, such as sodium carbonate, triethylamine, N,N-diisopropylethylamine or pyridine. The reaction is generally carried out at temperatures of room temperature to the refluxing temperature of the solvent and require from about 1-24 hours. The product can be isolated by techniques well known in the art, such as extraction, evaporation, and precipitation and can be purified by chromatography and recrystallization.
Alternately, for example, in an amine alkylation a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x80x94NHR8 is contacted in a reductive alkylation with a suitable aldehyde to give a compound of formula (5) in which R3 is xe2x80x94(CH2)mxe2x80x94Zxe2x80x94Q in which Z is xe2x80x94NR8xe2x80x94. A suitable aldehyde is one which transfers Q or protected Q as desired in the final product of formula (1), such as benzaldehyde and substituted benzaldehydes, The reaction is carried out in a suitable solvent, such as methanol, ethanol, tetrahydrofuran, or mixtures of methanol or ethanol and tetrahydrofuran. The reaction may be carried out in the presence of a drying agent, such as sodium sulfate or molecular sieves. The reaction is carried out in the presence of from 1.0 to 6.0 molar equivalents of a suitable reducing agent, such as, sodium borohydride or sodium cyanoborohydride with sodium cyanoborohydride being preferred. It may be advantageous to maintain the pH in the range of about 4 to 6. The reaction is generally carried out at temperatures of from 0xc2x0 C. to the refluxing temperature of the solvent. Generally, the reactions require 1 to 72 hours. The product can be isolated by techniques well known in the art, such as extraction, evaporation, and precipitation and can be purified by chromatography and recrystallization.
For example, in an amido formation a compound of formula (4a) in which R3xe2x80x3 is is xe2x80x94(CH2)mxe2x80x94CO2H is contacted with a suitable amine in an amide formation to give a compound of formula (5) in which R3 is xe2x80x94(CH2)mxe2x80x94Zxe2x80x94Q in which Z is amido. Such amide formation reactions using carboxy activation or suitable coupling agents are well known in the art and described above. A suitable amine, HNR8Q, gives rise to R8 and Q as desired in the final product of formula (1), such as methylamine, ethylamine, propylamine, butylamine, N-methyl benzylamine, benzyl xcex2-alanine, 4-(3-aminopropyl)morpholine, and the like.
For example, in an amide formation a compound of formula (4a) in which R3xe2x80x3 is is xe2x80x94(CH2)mxe2x80x94NHR8 is contacted with a suitable carboxylic acid in an amide formation to give a compound of formula (5) in which R3 is xe2x80x94(CH2)mxe2x80x94Zxe2x80x94Q in which Z is amide. Such amide formation reactions using carboxy activation or suitable coupling agents are well known in the art and described above. Suitable carboxylic acids, QC(O)xe2x80x94OH, are ones give rise to Q as desired in the final product of formula (1), such as benzoic acid, substituted benzoic acids, phenyl acetic acids, substituted phenylacetic acids, mono-t-butyl malonate, and the like.
For example, in a urea formation a compound of formula (4a) in which R3xe2x80x3 is is xe2x80x94(CH2)mxe2x80x94NHR8 is contacted with an appropriate isocyanate, Oxe2x95x90Cxe2x95x90Nxe2x80x94Q, to give a compound of formula (5) in which R3 is xe2x80x94(CH2)mxe2x80x94Zxe2x80x94Q in which Z is urea. An appropriate isocyanate is one which gives rise to Q as desired in the final product, such as phenyl isocyanate, substituted phenyl isocyanate, napthyl isocyanate, ethyl isocyanatoacetate, and the like. The reaction is carried out by adding an equivalent of, or a slight molar excess of, an appropriate isocyanate is added to a solution of a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x80x94NHR8 in a suitable solvent, such as diethyl ether, benzene, or toluene. The reaction is carried out at temperature of from about 0xc2x0 C. to the refluxing temperature of the solvent and require about 1-24 hours. The product can be isolated and purified by techniques well known in the art, such as filtration, extraction, evaporation, trituration, chromatography, and recrystallization.
For example, in an N-carbamoyl formation a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x80x94NHR8 is contacted with an appropriate chloroformate to give a compound of formula (5) in which R3 is xe2x80x94(CH2)mxe2x80x94Zxe2x80x94Q in which Z is N-carbamoyl. An appropriate chloroformate is one which gives rise to Q as desired in the final product of formula (1). Examples of chloroformates include benzyl chloroformate, naphthyl chloroformate, phenyl chloroformate, and substituted phenyl chloroformates, such as 4-chlorophenyl chloroformate, 4-methylphenyl chloroformate, 4-bromophenyl chloroformate, 4-fluorophenyl chloroformate, 4-methoxyphenyl chloroformate and the like. The reaction is carried out by adding an equivalent of, or a slight molar excess of, an appropriate chloro formate to a solution of a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x80x94NHR8 in a suitable solvent, such as toluene, tetrahydrofuran, dimethylformamide, dichloromethane, pyridine, or chloroform. The reaction is carried out in the presence of an excess of a suitable base, such as triethylamine, sodium carbonate, potassium bicarbonate, pyridine or N,N-diisopropylethylamine. The reaction is carried out at a temperature of from xe2x88x9270xc2x0 C. to the refluxing temperature of the solvent and generally requires from 30 minutes to 24 hours. The product can be isolated and purified by techniques well known in the art, such as extraction, evaporation, chromatography, and recrystallization.
For example, in an O-carbamoyl formation a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x88x921xe2x80x94CH2OH is contacted with an appropriate isocyanate, as defined above for urea formation, to give a compound of formula (5) in which R3 is xe2x80x94(CH2)mxe2x80x94Zxe2x80x94Q in which Z is O-carbamoyl. The reaction is carried out in a suitable solvent, such as diethyl ether, tetrahydrofuran, dimethylformamide, or acetonitrile. The reaction may be facilitated by the use of catalytic amount of a suitable base, such as sodium hydride, potassium hydride, or potassium t-butoxide. The reaction is generally carried out at temperatures of from xe2x88x9220xc2x0 C. to room temperature and require from about 1-24 hours. The product can be isolated by techniques well known in the art, such as extraction, evaporation, and precipitation and can be purified by chromatography and recrystallization.
For example, in a sulfonamide formation to prepare a compound in which R3 is xe2x80x94(CH2)mxe2x80x94SO2NR8xe2x80x94Y1, a compound of formula (4a) in which R3xe2x80x3 is xe2x80x94(CH2)mxe2x80x94NHR8 is contacted with an appropriate sulfonamide forming reagent. An appropriate sulfonamide forming reagent, such as a sulfonyl chloride, Y1S(O)2Cl, or sulfonyl anhydride, Y1(O)2Sxe2x80x94Oxe2x80x94S(O)2 Y1, is one which gives rise to Y1 as desired in the final product. Examples of appropriate sulfonamide forming reagents are, benzenesulfonyl chloride, 1-napthalenesulfonyl chloride, 2-napthalenesulfonyl chloride, dansyl chloride, N-morpholinylsulfonyl chloride, N-piperidinylsulfonyl chloride, 2,4,5-trichlorobenzenesulfonyl chloride, 2,5-dichlorobenzenesulfonyl chloride, 2,4,6-triisopropylbenzenesulfonyl chloride, 2-mesitylenesulfonyl chloride, 4-bromobenzenesulfonyl chloride, 4-fluorobenzenesulfonyl chloride, 4-chlorobenzenesulfonyl chloride, 4-methoxybenzenesulfonyl chloride, 4-t-butylbenzenesulfonyl chloride, p-toluenesulfonyl chloride, 2,3,4-trichlorobenzenesulfonyl chloride, 2,5-dimethoxybenzenesulfonyl chloride, 4-ethylbenzenesulfonyl chloride, 3,4-dimethoxybenzenesulfonyl chloride, 2,6-dichlorobenzenesulfonyl chloride, 3-bromobenzenesulfonyl chloride, 4-n-butylbenzenesulfonyl chloride, benzenesulfonic anhydride, 4-toluenesulfonic anhydride, and 2-mesitylenesulfonic anhydride. The reaction is carried out in a suitable solvent, such as tetrahydrofuran, dichloromethane, pyridine, or chloroform and in the presence of an excess of a suitable base, such as triethylamine, sodium carbonate, pyridine, or N,N-diisopropylethylamine. The reaction is carried out at a temperature of from xe2x88x9250xc2x0 C. to the refluxing temperature of the solvent. The reaction generally requires from 30 minutes to 24 hours. The product can be isolated and purified by techniques well known in the art, such as extraction, evaporation, chromatography, and recrystallization.
In Reaction Scheme D, step 3, a compound of formula (5) in which R3 is as desired in the final product of formula (1) undergoes a selective thiol deprotection to give a compound of formula (5a). Such selective thiol deprotections using suitable protecting groups are well known and appreciated in the art as discussed in Reaction Scheme C, step 1, above.
In Reaction Scheme D, step 4, a compound of formula (5a) undergoes a modification reaction to give a compound of formula (6) as described in Reaction Scheme C, step 2, above.
In Reaction Scheme D, step 5, a compound of formula (5), (5a), or (6) is deprotected to give a compound of formula (1) as discussed in Reaction Scheme C, step 4, above.
Alternate routes to the versatile intermediate of formula (6) are set forth below in Reaction Scheme E. 
In Reaction Scheme E, step 1a, a dipeptide of formula (2) is coupled with an appropriate acid derivative bearing R3 and xe2x80x94SR4 (compound of formula (3a1)) to give a compound of formula (6). Such coupling reactions are carried out in suitable solvents and using suitable bases and coupling agents, as required, and are well known and appreciated in the art and discussed above. The product of Reaction Scheme E, step 1a, can be isolated and purified by techniques well known in the art and described in Reaction Scheme A, step 1, above.
In step 1a, an appropriate compound of formula (3a1) is one in which R3 and R4 are a desired in the final product of formula (1) or gives rise after deprotection to R3 and/or R4 as desired in the final compound formula (1). In addition, an appropriate compound of formula (3a1) may also be one in which the stereochemistry at the R3 and xe2x80x94SR4 bearing carbon is as desired in the final product of formula (1). The activating group (A) is as described in Reaction Scheme A, step 1, above.
In Scheme B, step 1b, an appropriate carboxy protected amino acid derivative bearing R2 or protected R2 (compound of the formula (2a2)) is coupled with an appropriate acid derivative bearing R3 and xe2x80x94SR4 (compound of formula (3a2)), to give after carboxy deprotection (step 2), a compound of formula (4b). Such coupling reactions are carried out as discussed above. The product of Reaction Scheme B, step 1b, can be isolated and purified by techniques well known in the art and described above or can be used directly in step 2b.
In step 1b, an appropriate compound of the formula (2a2) is one in which R2 is as desired in the final compound of formula (1) or gives rise after deprotection to R2 as desired in the final compound of formula (1). In addition, an appropriate compound of the formula (2a2) may also be one in which the stereochemistry at the R2 bearing carbon is as desired in the final product of formula (1). The carboxy protecting group (Pg1xe2x80x2) is one which can be selectively removed in the presence of any protecting groups on R2, R3, and/or R4. The use of methyl, benzyl, and t-butyl for Pg1xe2x80x2 is preferred. An appropriate compound of formula (3a2) is one in which R3 and R4 are a desired in the final product of formula (1) or gives rise after deprotection to R3 and R4 as desired in the final compound formula (1). In addition, an appropriate compound of formula (3a2) may also be one in which the stereochemistry at the R3 and xe2x80x94SR4 bearing carbon is as desired in the final product of formula (1). The activating group (A) is as described in Reaction Scheme A, step 1, above.
In Reaction Scheme E, the product of step 1b in which Y is bromo preferably undergoes a displacement as described in Reaction Scheme C, steps 1 and 3 to give, after deprotection (step 2) a dipeptide of formula (4b) in which Y is protected thio for use in step 2b and subsequently step 3b.
In Reaction Scheme E, step 2b, the carboxy protecting group (Pg1xe2x80x2) of the product of coupling step 1b is selectively removed to give the dipeptide of formula (4b). Such selective carboxy deprotection reactions are well known and appreciated in the art. The product of Reaction Scheme E, step 2b, can be isolated and purified by techniques well known in the art, such as extraction, evaporation, salt formation, trituration, lyophilization, chromatography, and recrystallization or can be used directly in the following step.
In Reaction Scheme E, steps 3b, an appropriate carboxy protected amino acid derivative bearing R1 or protected R1 (compound of the formula (1a2)) is coupled with a dipeptide of formula (4b) to give a compound of formula (6). Such coupling reactions are carried out in suitable solvents and using suitable bases and coupling agents, as required, and are well known and appreciated in the art and discussed above.
An appropriate compound of the formula (1a2) is one in which R1 is as desired in the final compound of formula (1) or gives rise after deprotection to R1 as desired in the final compound of formula (1). In addition, an appropriate compound of formula (1a2) may also be one in which the stereochemistry at the R1 bearing carbon is as desired in the final product of formula (1). The carboxy protecting group (Pg1) is as defined in Reaction Scheme A, step 1, and into account, other protecting groups and subsequent reactions which may be required to provide the final compound of formula (1).
Alternate routes for preparing the compounds of formula (3b1) and formula (3b2) in which Y is bromo are presented in Reaction Schemes F.1 and F.2. 
In Reaction Scheme F.1, an appropriate xcex1-amino carboxylic acid of formula (8) is deaminobrominated to give a compound of formula (3b1) or formula (3b2)in which Y is bromo and A is xe2x80x94OH. An appropriate xcex1-amino carboxylic acid of formula (8), and protected forms thereof, is one which is one in which R3xe2x80x2 is R3 as desired in the final product of formula (1) or gives rise after deprotection to R3 as desired in the final product of formula (1). In addition, xcex1-amino carboxylic acid of formula (8) may also be one in which the stereochemistry at the R3xe2x80x2 bearing carbon gives rise after displacement to the stereochemistry as desired at that carbon in the final product of formula (1). Such appropriate xcex1-amino carboxylic acid of formula (8), are commercially available or may be readily prepared by techniques and procedures well known and appreciated by one of ordinary skill in the art. For example, L-alanine, D-alanine, L-valine, D-valine, D-norvaline, L-leucine, D-leucine, D-isoleucine, D-tert-leucine, glycine, L-glutamic acid, D-glutamic acid, L-glutamine, D-glutamine, L-lysine, D-lysine, L-ornithine, D-ornithine, (D)-(xe2x88x92)-2-aminobutyric acid, D-threonine, D-homoserine, D-allothreonine, D-serine, D-2-aminoadipic acid, D-aspartic acid, D-glutamic acid, D-lysine hydrate, 2,3-diaminopropionic acid monohydrobromide, D-ornithine hydrochloride, D,L-2,4-diaminobutyric acid dihydrochloride, L-meta-tyrosine, D-4-hydroxyphenylglycine, D-tyrosine, L-phenylalanine, D-phenylalanine, D,L-2-fluorophenylalanine, beta-methyl-D,L-phenylalanine hydrochloride, D,L-3-fluorophenylalanine, 4-bromo-D,L-phenylalanine, L-phenylalanine, L-phenylglycine, D-phenylglycine, D,L-4-fluorophenylalanine, 4-iodo-D-phenylalanine, D-homophenylalanine, D,L-2-fluorophenylglycine, D,L-4-chlorophenylalanine, and the like, are all commercially available and the methods in D. A. Evans, et al. J. Am. Chem. Soc., 112, 4011-4030 (1990); S. Ikegami et al. Tetrahedron, 44, 5333-5342 (1988); W. Oppolzer et al. Tet. Lets. 30, 6009-6010 (1989); Synthesis of Optically Active xcex1-Amino-Acids, R. M. Williams (Pergamon Press, Oxford 1989); M. J. O""Donnell ed.: xcex1-Amino-Acid Synthesis, Tetrahedron Symposia in print, No. 33, Tetrahedron 44, No. 17 (1988); U. Schxc3x6llkopf, Pure Appl. Chem. 55, 1799 (1983); U. Hengartner et al. J. Org. Chem., 44, 3748-3752 (1979); M. J. O""Donnell et al. Tet. Lets., 2641-2644 (1978); M. J. O""Donnell et al. Tet. Lets. 23, 4255-4258 (1982); M. J. O""Donnell et al. J. Am. Chem. Soc., 110, 8520-8525 (1988).
The deaminobromination described in Reaction Scheme F.1 can be performed utilizing conditions described in Compagnone, R. S. and Rapoport, H., J. Org. Chem., 51, 1713-1719 (1986); U.S. Pat. No. 5,322,942, issued Jun. 21, 1994; Overberger, C. G. and Cho, I., J. Org. Chem., 33, 3321-3322 (1968); or Pfister, K. et al., J. Am. Chem. Soc., 71, 1096-1100 (1949).
For example, an xcex1-amino carboxylic acid of formula (8) and a suitable bromide, such as hydrogen bromide or potassium bromide in acidic solution, such as sulfuric acid, is treated with sodium nitrite. The reaction temperature is carried out a temperatures of from about xe2x88x9225xc2x0 C. to about ambient temperature and require about 1 to 5 hours. The product can be isolated and purified by techniques well known in the art, such as acidification, extraction, evaporation, chromatography, and recrystallization to give the compound of formula (3b1) or formula (3b2)in which Y is bromo and A is xe2x80x94OH. The product can be isolated and purified by techniques well known and appreciated in the art, such as acidification, basification, filtration, extraction, evaporation, trituration, chromatography, and recrystallization. 
In Reaction Scheme F.2, an appropriate carboxylic acid of formula (9) is brominated to give compound of formula (3b1) or formula (3b2) in which Y is bromo and A is xe2x80x94OH. An appropriate carboxylic acid of formula (9), and protected forms thereof, is one which is one in which R3xe2x80x2 is R3 as desired in the final product of formula (1) or gives rise after deprotection to R3 as desired in the final product of formula (1). In addition, carboxylic acid of formula (9) may also be one in which the stereochemistry at the R3xe2x80x2 bearing carbon gives rise after displacement to the stereochemistry as desired at that carbon in the final product of formula (1).
For example, a mixture of a carboxylic acid of formula (9) and dry red phosphorous are treated dropwise with bromine at temperature ranging from about xe2x88x9220xc2x0 to about 10xc2x0 C. The reaction mixture is then warmed to room temperature and then heated to about 80xc2x0 C. for about 2-5 hours. The reaction mixture is then cooled to room temperature, poured into water containing sodium bisulfite, and neutralized using solid sodium carbonate. The aqueous layer is extracted and acidified with a suitable acid, such as concentrated hydrochloric acid, The precipitate is collected by filtration and dried to give the compound of formula (3b1) or formula (3b2)in which Y is bromo and A is xe2x80x94OH. The product can be isolated and purified by techniques well known and appreciated in the art, such as acidification, basification, filtration, extraction, evaporation, trituration, chromatography, and recrystallization.
Compounds of formula (8) and (9) in which R3xe2x80x2 is a xe2x80x94(CH2)mxe2x80x94W for use in Reaction Schemes F.1 and F.2 are prepared according to Reaction Scheme G.1 and G.2. 
In Reaction Scheme G.1 an appropriate xcfx89-amino carboxylic acid of formula (11) is converted to an compound of formula (9) in which R3xe2x80x2 is Wxe2x80x94(CH2)mxe2x80x94. An appropriate xcfx89-amino carboxylic acid of formula (11) is one in which m is as desired in the final product of formula (1) and are readily available in the art. For example, the reaction is carried out in a suitable polar solvent, such as water, ethanol, diethyl ether, tetrahydrofuran, or a water/ethanol solvent mixture using a suitable base, such as sodium carbonate and N-carbethoxyphthalimide. The reaction mixture is typically stirred at about ambient temperature for 1-5 hours. The product can be isolated and purified by techniques well known in the art, such as acidification, extraction, evaporation, chromatography, and recrystallization to give the desired compound of formula (9) in which R3xe2x80x2 is Wxe2x80x94(CH2)mxe2x80x94. 
Reaction Scheme G.2, step 1, an appropriate xcex1,xcfx89-diamino acid of formula (12) undergoes a selective N-xcex1-protection to give an N-xcex1-protected-107-diamino acid of formula (13). An appropriate xcex1,xcfx89-diamino acid of formula (12) is one in which m is as desired in the final product of formula (1).
For example, a selective N-xcex1-protection of a suitable xcex1,xcfx89-diamino acid, such as L-lysine (formula 12 in which m is 4), is accomplished by masking the xcfx89-amino group by formation of a benzylidene imine. The benzylidene imine is formed by dissolving L-lysine monohydrochloride in lithium hydroxide and cooling the solution to a temperature ranging from about 0xc2x0 to 10xc2x0 C. Freshly distilled benzaldehyde is then added and the solution is shaken. N-xcfx89-benzylidene-L-lysine is recovered by filtration and evaporation. The xcex1-amino group of the N-xcfx89-benzylidene-L-lysine then undergoes protection, such as the introduction of a Cbz or t-Boc group, followed by hydrolytic cleavage of the imine in situ to give N-xcex1-benzyloxy-carbonyl-L-lysine. Accordingly, N-xcfx89-benzylidene-L-lysine is added to a mixture of sodium hydroxide and ethanol, cooled to a temperature of from about xe2x88x925xc2x0 to about xe2x88x9225xc2x0 C. Then, precooled solutions of benzyloxycarbonyl chloride in a solvent, such as ethanol, is added to the reaction mixture. The temperature is maintained in a range of from about xe2x88x9210xc2x0 to about xe2x88x9225xc2x0 C. during the course of addition, and may allowed to rise afterwards. The reaction mixture is then acidified using a suitable acid, such as precooled hydrochloric acid, and N-xcex1-benzyloxycarbonyl-L-lysine, which corresponds to formula (13) where m is 4, is recovered by filtration evaporate and recrystallization.
In Reaction Scheme G.2, step 2, N-xcex1-benzyloxycarbonyl-L-lysine or other compounds of formula (13) is converted to xcfx89-phthalimido-xcex1-benzyloxycarbonyl-L-lysine or other xcfx89-phthalimido-xcex1-aminoprotected carboxylic acid of formula (14) by the method described in Reaction Scheme G.1, above.
In Reaction Scheme G.2, step 3, the xcfx89-phthalimido-xcex1-aminoprotected carboxylic acid of formula (14) is deprotected to give compound of formula (8) in which R3xe2x80x2 is Wxe2x80x94(CH2)mxe2x80x94.
For example, xcfx89-phthalimido-xcex1-benzyloxycarbonyl-L-lysine is contacted with hydrogen in the presence of a hydrogenation catalyst, such as 10% palladium/carbon. The reactants are typically contacted in a suitable solvent mixture such as ethanol, methanol, water, ethanol/water mixtures, or methanol/water mixtures. The reactants are typically shaken under a hydrogen atmosphere of 35-45 psi at room temperature for a period of time ranging from 5-24 hours. The product is typically recovered by filtration and evaporation of the solvent.
A route for preparing the compounds of formula (3b1) and formula (3b2) in which Y1 is protected thio is presented in Reaction Reaction Scheme H. The reagents and starting materials are readily available to one of ordinary skill in the art. In Reaction Reaction Scheme H all substituents, unless otherwise indicated, are as previously defined. 
In Reaction Scheme H, step 1, a bromoacetate of formula (15) is contacted with an appropriate thiol to give a protected acetic acid ester of formula (17). In a bromoacetate of formula (15) Pg5 is a protecting group, such as methyl, ethyl, t-butyl, and benzyl. An appropriate thiol is one which gives rise to a protected thio group, Y, in the product of formula (3b). The use of 4-methoxybenzylmercaptan is preferred.
For example, a bromoacetate of formula (15) is contacted with an appropriate thiol in a suitable organic solvent, such as dimethylformamide. Advantageously, the solvent is degassed. The reaction is carried out using a suitable base, such as sodium hydroxide, triethylamine, or N,N-diisopropylethylamine. The reaction is carried out at temperatures of from about xe2x88x9250xc2x0 to about ambient temperature and requires about 1 to 72 hours. The protected acetic acid ester of formula (17) can be isolated and purified by methods well known and appreciated in the art, such as extraction, evaporation, chromatography, and distillation, and recrystallization.
In Reaction Reaction Scheme H, step 2, the protected acetic acid ester of formula (17) is alkylated with an appropriate akylating agent to give a compound of formula (18). In Reaction Reaction Scheme H, step 2, an appropriate alkylating agent is one which transfers R3xe2x80x2 which is R3 as desired in the final product of formula (1) or gives rise after deprotection to R3 as desired in the final product of formula (1) or gives rise to R3xe2x80x3 as defined in Reaction Scheme D, step 1. Appropriate alkylating agents include alkylhalides, such as methyl iodide, methyl bromide, ethyl bromide, propyl bromide, propyl chloride, butyl bromide, butyl chloride, and the like; benzyl bromide, benzyl chloride, substituted benzyl bromide, substituted benzyl chloride, ethyl bromoacetate, t-butyl bromoaceate, ethyl 3-chloropropionate, ethyl 3-bromopropionate, ethyl 5-bromovalerate, ethyl 4-bromobutyrate, 3-chloropropionamide, 2-bromoethylbenzene, substituted 2-bromoethylbenzene, 1-chloro-3-phenylpropane, 1-bromo-4-phenylbutane, and the like, N-(2-bromoethyl)phthalimide, N-(3-bromopropyl)phthalimide, N-(4-bromobutyl)phthalimide, and the like; 1-bromo-2-phenylethane, 1-bromo-3-phenylpropane, 1-bromo-4phenylbutane, and the like.
For example, a protected acetic acid ester of formula (17) is alkylated with an appropriate alkylating agent. The reaction is carried out in a suitable solvent, such as diethyl ether) tetrahydrofuran, dimethylformamide, and toluene using a suitable base, such as sodium hydride, potassium hydride, potassium t-butoxide, lithium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, potassium bis(trimethylsilyl)amide, or lithium diisopropylamide. The reaction is generally carried out at temperatures of about xe2x88x9270xc2x0 C. to about room temperature and require from about 1-24 hours. The product can be isolated by techniques well known in the art, such as extraction, evaporation, and precipitation and can be purified by chromatography and recrystallization.
In Reaction Scheme H, step 3, the compound of formula (18) the carboxy protecting group Pg5 is selectively removed to give a compound of formula (3b) in which Y is protected thio. Such deprotection of esters to acids in the presence of suitable thio protecting groups are well known and appreciated in the art.